Introduction: Testosterone (T) therapy is able to promote biochemical, body composition and Cardiovascular (CV) alterations in Transgender Men (TM). However, existing data concern TM between 18 and 50 years old. Objective: To describe the first year of usage of T in a 52-year-old TM: Hormonal and biochemical changes, body composition and CV aspects during exercise. Methods: Medical record review was accessed as well as laboratorial and image exams performed during the first year of T use. Results: TM, 52-years-old, no previous usage of T, initiated testosterone undecanoate 1000 mg. A second dose was given 6 weeks after the first one and then every 12 weeks. By the third month of treatment, the highest level of T was noted (586 ng/dL). After 7 months of treatment, hemoglobin and hematocrit reached their highest levels, 16.3 g/dL and 47.1% respectively, and dropped to 15.5 g/dL and 43.6% by the twelfth month. LDLc increased 31% by the seventh month and returned to baseline by the twelfth month. Bone density increased 3.1% in lumbar spine (L1-L4) and 2.7% in femoral neck. The Muscle Mass (MM) increased 10.9% in one year. Pretreatment Ergometric Test (ET) showed increase in Systolic Blood Pressure (SBP) of 38.4% (130 to 180 mmHg) during exertion and decrease of >100% in the sixth minute of passive recovery. Heart Rate (HR) increased 73 bpm during ET and returned to baseline at the third minute of rest (reduction of 72 bpm). One year post treatment results showed that SBP increased 61.5% (130 to 210 mmHg) and decreased >100% after six minutes of rest. HR increased 67 bpm during exertion and decreased by 75 bpm at the third minute of rest. Discussion: A meta-analysis covering studies lasting 6 to 12 months with TM using testosterone undecanoate 1000 mg every 12 weeks showed that the increase of Hb and HT ranges from 4.9% to 12.5% and 4.4% to 17.6%, respectively, which is much lower than the averages presented in our case (23 and 27%, respectively). Progressive increase of LDLc up to 18.7% is described in the literature. The lowest drop in fat mass is described in young TM. Young cis women and men present an increase in SBP during ET around 34.0% and 39.8%, respectively, and in the third minute of recovery a drop around 20.6% and 23.4%. HR drops from 60.5 to 64.53 bpm in the third minute of rest and higher recoveries are associated with better parasympathetic reactivation and lower mortality. Conclusion: TM over 50 years old seems to present higher increase of Hb/HT and decrease of HDLc when compared to younger TM. The lowest HR increase and highest variation of SBP during ET after 1 year of T might be a consequence of enlarged cardiac chambers, increased systolic volume and peripheral vascular resistance.